Conceptual model of groundwater and river water interactions in Cikapundung riverbank, Bandung, West Java

Cikapundung river holds a very strategic role as one of the water supply source for Bandung, but the water quality is decreasing over the years. This degradation has also influenced the groundwater in its riverbank. This paper discusses our effor to build a conceptual model to reconstruct previous analytical model which was built in 1997. The base map was built using a total of 32 scenes of WorldView-2 image, combined with Aster image. The dimension of the model was one layer model with elevation (Z) 400 to 2200 m, 361 rows and 454 columns, covering the area of 21.6 x 27.2 km2. Two types of property hydrogeology were defined based on the existing geological maps: Volcanic breccias and, Sand and clay intercalations. The parameterization of the stream was divided into two segments: Curug Dago to Viaduct, Viaduct to Dayeuhkolot. Initial head were observed at: 17 dug wells, 24 river points, and two spring points in 2013. All parameters accommodated by software SWS visual MODFLOW flex 2012 that used three-dimension mathematic equation in steady state to build a conceptual model. Model has been calibrated and showed an appropriateness with dug wells and springs with correlation coefficient of 0.92 and water balance in 0.01 steady state condition (2040 m3).The conceptual model successfully replicates the previous analytical model, showing three segments of water interactions: no flow at segment Maribaya to Curug Dago, combination of effluent and influent flow at segment Curug Dago to Viaduct, and influent flow Viaduct to Dayeuhkolot. However, the model shows some local variations that was not spotted in the previous model.